The present invention relates to gas turbines, and, in particular, to a resilient seal for reducing air leakage and improving turbine engine efficiency.
In industrial gas turbines, shroud segments are fixed to turbine shell hooks in an annular array about the turbine rotor axis to form an annular shroud radially outwardly of and adjacent to the tips of buckets forming part of the turbine rotor. The inner wall of the shroud defines part of the gas path. Conventionally, the shroud segments are comprised of inner and outer shrouds provided with complimentary hooks and grooves adjacent to their leading (forward) and trailing (aft) edges for joining the inner and outer shrouds to one another. The outer shroud is, in turn, secured to the turbine shell or casing. Typically, each shroud segment has one outer shroud and two or three inner shrouds.
A few designs have been used for configuring inner shrouds. One conventional configuration is illustrated in FIG. 1 and referred to as the opposite hook design. As can be seen, in the traditional opposite hook design, the inner shroud 10 includes leading and trailing edge hooks 12,14 projecting in opposite directions. The outer shroud 16 retains the inner shroud with leading and trailing mutually facing hooks 18,20.
This conventional shroud hook arrangement can limit the surface 22 available for impingement cooling and requires additional, less efficient convectional cooling of the inner shroud. In addition, the axial load surface between the inner and outer shrouds is always one sided; the axial load surface is either at the forward side or at the aft side. While the loaded surface provides a sealing function for the post impingement cavity 24 of the shroud assembly, the other end of the shroud assembly is unsealed.
By making the inner shroud 110 C-shaped with the hooks facing one another, as for example in U.S. Pat. No. 6,402,466, the disclosure of which is incorporated herein by reference, and as schematically shown in FIG. 2, the impingement cooling can cover the entire inner side 122 of the inner shroud. However, post impingement cavity 124 leakage undesirably reduced the cooling efficiency, increases the usage of cooling air, and deteriorates performance.